Abstract
Today, fuel-air mixtures in internal combustion engines are ignited by an electric spark discharge.
Therefore, we call them “spark ignition engines”. However, torch-hole flame (1794～) or hot-tube
(1855～) were the main ignition sources of early internal combustion engines, namely, flames were used.
The paper presents the historical changes of the ignition method of engines and the recent enhancement
method of ignition including laser ignition.
